§1.1 Field of the Invention
The present invention concerns methods, apparatus and data structures for aggregating traffic, which may originate from various media transport types, for presentation to a router, such as an access router of a network. Further, the traffic aggregation performed by the present invention may be done such that customers can be identified and such that customer device addressing information is available. Moreover, the traffic aggregation performed by the present invention may be done such that the service provided to a group of customers may be monitored; multicast groups are secure; and the access router can control access to services, facilitate virtual private networks, and facilitate the provision of different quality of service and/or class of service levels.
§1.2 Related Art
The description of art in this section is not, and should not be interpreted to be, an admission that such art is prior art to the present invention.
§1.2.1 Communications Protocol Stack
Although networking software and network reference models are known to those skilled in the art, they are introduce here for the reader's convenience.
To reduce their complexity, networks may be organized as a series of layers, each one built upon the one below it as shown in FIG. 1. Each layer functions to offer certain services to the higher layer, thereby shielding those higher layers from the details of how the offered services are actually implemented. The entities comprising the corresponding layers on different machines are called “peers”. Such peers use rules and conventions, also referred to as the layer n protocol, to communicate with each other as depicted by the dashed lines in FIG. 1. Actually, no data are directly transferred from layer n on one machine to layer n on another machine. Rather, in the machine transmitting the data, each layer passes data and control information to the layer immediately below it, until the lowest layer (layer 1) is reached. Below layer 1, is a physical medium 110 through which actual communications take place. At the machine receiving the data, each layer passes data and control information to the layer immediately above it until the highest layer is reached. Thus, referring to FIG. 1, actual communications take place via the solid lines and the physical medium 110, while virtual peer-to-peer communications occur via the dashed lines.
Still referring to FIG. 1, interfaces are arranged between adjacent layers. Each of these interfaces defines primitive operations and services that the lower layer offers to the upper layer.
The set of layers and protocols may be referred to as a “network architecture”. A list of protocols used by a system, one protocol per layer, may be referred to as a “protocol stack” or “protocol suite”.
§1.2.2 Network Architecture Reference Models
FIG. 2 illustrates a comparison of the Open Systems Interconnection (or “OSI”) reference model 210 for network architectures and the transfer control protocol/Internet protocol (or “TCP/IP”) reference model 220 for network architectures. Although those skilled in the art will be familiar with both reference models, each is introduced below for the reader's convenience.
§1.2.2.1 The OSI Reference Model
As shown in FIG. 2, the OSI reference model 210 has seven (7) distinct layers; namely, (i) a physical layer 211, (ii) a data link layer 212, (iii) a network layer 213, (iv) a transport layer 214, (v) a session layer 215, (vi) a presentation layer 216, and (vii) an application layer 217. Each layer is briefly introduced below.
The physical layer 211 deals with transmitting raw bits over a communications channel. Thus, the physical layer is typically concerned with mechanical, electrical, optical, and procedural interfaces, as well as the physical transmission medium (e.g., twisted copper pair, co-axial cable, optical fiber, etc.) that lies below the physical layer.
The data link layer 212 functions to transform a raw communications facility into a line that appears free from undetected transmission errors to the network layer 213. The data link layer 212 does this by having the sending host segment its data into “data frames”, transmitting these frames to the receiving host, and processing “acknowledgement frames” sent back from the receiver.
The network layer 213 functions to control the operation of a subnetwork between the hosts and controls the routing of packets between the hosts.
The transport layer 214 functions to accept data from the session layer 215 and segment this data into smaller units, if necessary, for use by the network layer 213. The transport layer 214 also determines a type of service (e.g., error-free, point-to-point) to provide to the session layer 215. Further, the transport layer 214 controls the flow of data between hosts. The transport layer 214 is a true “end-to-end” layer, from source host to destination host, since a program on the source machine converses with a similar program on the destination machine, using message headers and control messages.
The session layer 215 functions to allow different machines to establish sessions between them. The session layer 215 may manage dialog control and maintain synchronization.
The presentation layer 215 concerns the syntax and semantics of information transmitted.
The application layer 216 may function to define network virtual terminals that editors and other programs can use, and to transfer files.
§1.2.2.2 The TCP/IP Model
In recent decades, and in the past five (5) to ten (10) years in particular, computers have become interconnected by networks by an ever increasing extent; initially, via local area networks (or “LANs”), and more recently via LANs, wide area networks (or WANs) and the Internet. In 1969, the Advanced Research Projects Agency (ARPA) of the U.S. Department of Defense (DoD) deployed ARPANET as a way to explore packet-switching technology and protocols that could be used for cooperative, distributed, computing. Early on, ARPANET was used by the TELNET application that permitted a single terminal to work with different types of computers, and by the file transfer protocol (or “FTP”) which permitted different types of computers to transfer files from one another. In the early 1970s′, electronic mail became the most popular application which used ARPANET.
This packet switching technology was so successful, that the ARPA applied it to tactical radio communications (Packet Radio) and to satellite communications (SATNET). However, since these networks operated in very different communications environments, certain parameters, such as maximum packet size for example, were different in each case. Thus, methods and protocols were developed for “internetworking” these different packet switched networks. This work lead to the transmission control protocol (or “TCP”) and the internet protocol (or “IP”) which became the TCP/IP protocol suite. Although the TCP/IP protocol suite, which is the foundation of the Internet, is known to those skilled in the art, it is briefly described below for the reader's convenience.
As shown in FIG. 2, the TCP/IP reference model 220 includes a physical layer 221, a network access layer 222, an internet layer 223, a transport layer 224, and an application layer 225. Each of these layers is briefly introduced below.
The physical layer 221 defines the interface between a data transmission device (e.g., a computer) and a transmission medium (e.g., twisted pair copper wires, co-axial cable, optical fiber, etc.). It specifies the characteristics of the transmission medium, the nature of the signals, the data rate, etc.
The network access layer 222 defines the interface between an end system and the network to which it is attached. It concerns access to, and routing data across, a network. Frame relay is an example of a network access layer.
The internet layer 223 functions to permit hosts to inject packets into any network and have them travel independently to the destination machine (which may be on a different network). Since these packets may travel independently, they may event arrive in an order other than the order in which they were sent. Higher layers can be used to reorder the packets. Thus, the main function of the internet layer 320 is to deliver (e.g., route) IP packets to their destination.
The transport layer 224 is an end-to-end protocol. For example, the transmission control protocol (or “TCP”) is a reliable connection-oriented protocol that allows a byte stream originating on one machine to be delivered, without error, on any other machine on the Internet. More specifically, the TCP protocol fragments an incoming data stream into discrete messages, each of which is passed to the internet layer 223. At the destination, the TCP protocol reassembles the received messages into an output stream.
The TCP/IP model 220 does not have session and presentation layers. Instead, an application layer 225 contains all of the higher-level protocols that are used to support various types of end use applications (e.g., the simple mail transfer protocol (or “SMTP”) for e-mail, the file transfer protocol (or “FTP”), etc.).
The TCP/IP model does not define what occurs below the internet layer 223, other than to note that the host has to connect to the network using some protocol so that it can send IP packets over it. This protocol varies from host to host and network to network.
Basically, each of the layers encapsulates, or converts, data in a higher layer. For example, referring to FIG. 4, user data 400 as a byte stream is provided with a TCP header 402 to form a TCP segment 410. The TCP segment 410 is provided with an IP header 412 to form an IP datagram 420. The IP datagram 420 is provided with a network header 422 to define a network-level packet 430. The network-level packet 430 is then converted to radio, electrical, optical (or other) signals sent over the transmission medium at a specified rate with a specified type of modulation.
The TCP header 402, as illustrated in FIG. 5, includes at least twenty (20) octets (i.e., 160 bits). Fields 502 and 504 identify ports at the source and destination systems, respectively, that are using the connection. Values in the sequence number 506, acknowledgement number 508 and window 516 files are used to provide flow and error control. The value in the checksum field 518 is used to detect errors in the TCP segment 410.
FIGS. 6A and 6B illustrate two (2) alternative IP headers 412 and 412′, respectively. Basically, FIG. 6A depicts the IP protocol (Version 4) that has been used. FIG. 6B depicts a next generation IP protocol (Version 6) that, among other things, provides for more source and destination addresses.
More specifically, referring to FIG. 6A, the four (4) bit version field 602 indicates the version number of the IP, in this case, version 4. The 4-bit Internet header length field 604 identifies the length of the header 412 in 32-bit words. The 8-bit type of service field 606 indicates the service level that the IP datagram 420 should be given. The 16-bit total length field 608 identifies the total length of the IP datagram 420 in octets. The 16-bit identification field 610 is used to help reassemble fragmented user data carried in multiple packets. The 3-bit flags field 612 is used to control fragmentation. The 13-bit fragment offset field 614 is used to reassemble a datagram 420 that has become fragmented. The 8-bit time to live field 616 defines a maximum time that the datagram is allowed to exist within the network it travels over. The 8-bit protocol field 618 defines the higher-level protocol to which the data portion of the datagram 420 belongs. The 16-bit header checksum field 620 permits the integrity of the IP header 412 to be checked. The 32-bit source address field 322 contains the IP address of the sender of the IP datagram 420 and the 32-bit destination address field contains the IP address of the host to which the IP datagram 120 is being sent. Options and padding 626 may be used to describe special packet processing and/or to ensure that the header 412 is a complete multiple of 32-bit words.
Referring to FIG. 6B, the four (4) bit version field 602 indicates the version number of the IP, in this case, version 6. The 4-bit priority field 628 enables a sender to prioritize packets sent by it. The 24-bit flow label field 630 is used by a source to label packets for which special handling is requested. The 16-bit payload length field 632 identifies the size of data carried in the packet. The 8-bit next header field 634 is used to indicate whether another header is present and if so, to identify it. The 8-bit hop limit field 636 serves to discard the IP datagram 420 if a hop limit (e.g., the number of times the packet is routed) is exceeded. Also provided are 128-bit source and destination address fields 322′ and 324′, respectively.
Having described the TCP/IP protocol stack 220, the routing of a TCP/IP packet is now described.
A TCP/IP packet is communicated over the Internet (or any internet or intranet) via routers. Basically, routers in the Internet use destination address information (Recall fields 624 and 624′.) to forward packets towards their destination. Routers interconnect different networks. More specifically, routers accept incoming packets from various connected networks, use a look-up table to determine a network upon which the packet should be placed, and routes the packet to the determined network.
FIG. 7, which includes FIGS. 7A through 7C, illustrates the communication of data from a sender, to a receiver, using the TCP/IP protocol stack. Referring first to FIG. 7A, an application protocol 702 prepares a block of data (e.g., an e-mail message (SMTP), a file (FTP), user input (TELNET), etc.) 400 for transmission. Before the data 400 are sent, the sending and receiving applications agree on a format and encoding and agree to exchange data (Recall, e.g., the peer-to-peer communications depicted with dashed lines in FIG. 1.). If necessary, the data are converted (character code, compression, encryption, etc.) to a form expected by the destination device.
The TCP layer 704 may segment the data block 400, keeping track of the sequence of segments. Each TCP segment 410 includes a header 402 containing a sequence number (recall field 506) and a frame check sequence to detect errors. A copy of each TCP segment is made so that if a segment is lost or damaged, it can be retransmitted. When an acknowledgement of safe receipt is received from the receiver, the copy of the segment is erased.
The IP layer 706 may break the TCP segment into a number of datagrams 420 to meet size requirements of networks over which the data will be communicated. Each datagram includes the IP header 412.
A network layer 708, such as frame relay for example, may apply a header and trailer 422 to frame the datagram 420. The header may include a connection identifier and the trailer may contain a frame check sequence for example. Each frame 430 is then transmitted, by the physical layer 710, over the transmission medium as a sequence of bits.
FIG. 7B illustrates the operation of the TCP/IP protocol stack at a router in the network. The physical layer 712 receives the incoming signal 430 from the transmission medium and interprets it as a frame of bits. The network (e.g., frame relay) layer 714 then removes the header and trailer 422 and processes them. A frame check sequence may be used for error detection. A connection number may be used to identify the source. The network layer 714 then passes the IP datagram 420 to the IP layer 718.
The IP layer examines the IP header 412 and makes a routing decision (Recall the destination address 324, 324′). A local line control (or “LLC”) layer 720 uses a simple network management protocol (or “SNMP”) and adds a header 750 that contains a sequence number and address information. Another network layer 722 (e.g., media access control (or “MAC”)) adds a header and trailer 760. The header may contain address information and the trailer may contain a frame check sequence. The physical layer 724 then transmits the frame 450 over another transmission medium.
FIG. 7C illustrates the operation of the TCP/IP protocol stack at a receiver. The physical layer 732 receives the signals from the transmission medium and interprets them as a frame of bits. The network layer 734 removes the header and trailer 760 and processes them. For example, the frame check sequence in the trailer may be used for error detection. The resulting packet 440 is passed to the transport layer 736, which processes the header 750 for flow and error control. The resulting IP datagram 420 is passed to the IP layer 738, which removes the header 412. Frame check sequence and other control information may be processed at this point.
The TCP segment 410 is then passed to the TCP layer 740, which removes the header 402 and may check the frame check sequence. (In the event of a match, the match is acknowledged and in the event of a mismatch, the packet is discarded.) The TCP layer 740 then passes the data 400 to the application layer 742. If the user data was segmented (or fragmented), the TCP layer 740 reassembles it. Finally, the application layer 742 performs any necessary transformations, such as decompression and decryption for example, and directs the data to an appropriate area of the receiver, for use by the receiving application.
§1.3 Expected Drivers of Future Network Design
The present inventors believe that most of the world's networks are, or will be, based on the Internet Protocol (or “IP”). There are at least three (3) assumptions underlying this belief. First, IP separates applications (or services) from transport (e.g., data link technology). The present inventors believe that value added services will be IP-based, due in part to favorable price-performance curves of IP access technology and the way in which IP can inter-operate with other technologies. Second, IP quality of service (or “QoS”) is emerging. These QoS mechanisms can be applied to the specific applications and services (e.g., audio-visual multicast, conferencing, high speed access such as via DSL, IP derived lines, IP telephony, IP fax, IP Centrex, Internet service provider (or “ISP”) services such as e-mail, Internet access, authorization, authentication and accounting, and billing, and unified messaging) of individual customers. Various types of applications may demand various levels of quality of service. For example, a voice over Internet application may require low delays, but may tolerate some packets being dropped, to the extent that such dropped packets cannot be perceived or are not annoying to users. This is because it would be pointless to retransmit erroneous packets in such a real-time application. Data transport may tolerate delays but will not tolerate transmission errors. Video over the Internet will require high bandwidth but may tolerate some dropped packets (again, to the extent that such dropped packets would not be perceived by, or be annoying to, a customer). Third, data competitive (or certified) local exchange carriers (or “DLECs”)—that is, companies that provide high speed access to the Internet—currently provide integrated IP services using asynchronous transfer mode (or “ATM”) transport. The present inventors believe that as lower cost link layer technologies are deployed, such as gigabit Ethernet for example, DLECs will abandon ATM.
With this background in mind, the present inventors propose a multi-service local access and transport area (or “LATA”) IP network with the following two (2) design goals in mind. First, it should be simple for existing and potential customers to use the proposed LATA IP network. Second, the LATA IP network should be robust and flexible, while having a low operating cost. The present inventors believe that customer simplicity can be achieved by (i) eliminating or minimizing changes to existing layer 1 and 2 customer interfaces (so that existing customers may be retained) and (ii) providing new, low cost, high value IP interfaces to customers (such as Fast Ethernet and Gigabit Ethernet). The present inventors further believe that the LATA IP network can be robust, flexible, and have low operating costs by (i) minimizing complexity (by isolating subsystems with different component technologies and separating application functionality from the underlying transport network), (ii) minimizing operations, (iii) providing the ability to route traffic for services which have different topology and volume assumptions, and (iv) ensuring reliability by using off-the-shelf components and standard protocols (thereby eliminating customization) and by providing redundant equipment and facilities.
The LATA IP network envisioned by the present inventors may use off-the-shelf routers. These routers may function to (i) provide access to customers, (ii) interconnect networks, and/or (iii) provide routing between intranetwork elements. Thus, the LATA IP network may use three (3) different types of routers. In the LATA IP network, access routers may be distributed towards the edge of the network and may provide individual customer IP interfaces into the network. Thus, the access router may act as a universal IP edge device for diverse customer access methods. Interconnection routers may be centralized with the IP LATA and may provide a small number of (e.g., high bandwidth) external interfaces to the other carrier's (or enterprise customer's) network(s). Finally, routers may be deployed, as needed, throughout the IP LATA to consolidate traffic and to minimize the cost of traffic transport between elements of the IP LATA.
§1.3.1 Challenges in Accessing an Edge Router
One aspect of the present invention concerns the challenge of aggregating a number of physical connections from a number of potentially diverse customers, for connection to an edge router. For example, standards-based routers that can handle 128 Gbps bandwidth are currently available. However, such routers cannot accommodate the physical connections of the tens or hundreds of thousands of individual services that they could otherwise accommodate. For example, assuming that customers had a very high end 10 or 100 Mbps service (or communications access links capable of such service levels), such routers could process the data flow from 12,800 or 1,280 customers, respectively, but could not accommodate those numbers of physical connections. Naturally, a larger number of physical connections (e.g., for lower end service(s)) could not be accommodated.
Digital subscriber line access multiplexers (or “DSLAMs”) may be used to concentrate traffic in asynchronous digital subscriber line (or “ADSL”) implementations by using time division multiplexing. Basically, a DSLAM can accept twisted copper pairs supporting ADSL service and provide them on virtual channels on a shared common communications medium, such as an OC3 (e.g., 155.52 Mbps) fiber channel. However, an asynchronous transfer mode (or “ATM”) switch is needed to switch these physical connections to virtual channels, thereby necessitating an ATM switch port for each customer connection. Aside from physically requiring a lot of space, using a DSLAM for this purpose would be expensive on a per port basis. Thus, improved techniques are needed to aggregate physical connections, for example, for presentation to an access router.
Another aspect of the present invention concerns the challenge of separating customer services from customer access technologies (e.g., DSL, Frame Relay, Gigabyte Ethernet). In this way, a variety of services could be provided to a variety of potential customers without regard for the way in which such potential customers access the IP LATA network.